1. Field of the Invention
The present invention pertains to voice over the Internet technology.
2. Related Art
a. Voice Over the Internet
Worldwide deregulation and packet-switched technology have brought dramatic changes to the telecommunications industry. Voice communication over packet-switched networks, such as, the Internet, is now in demand. Voice over the Internet technology is now available which integrates a public switched telephone network (PSTN) and the Internet. Voice over the Internet technology is also referred to as, Voice over Internet Protocol (VoIP), Voice over Network (VON), Internet Telephony, and Telephony over the Internet. See, e.g., G. Held, Voice over Data Networks, Mc-Graw-Hill Series on Computer Communications (McGraw-Hill Publ.: 1998), entire book; and T. Sheldon, Encyclopedia of Networking, Electronic Edition, (Mcgraw-Hill Publ.: 1998), pp. 1047-1050. Both of these references are incorporated in their entirety herein by reference. A PSTN is also referred to as a plain old telephone system (POTS). A PSTN can include transmission components (links), switching components (nodes), and billing facilities. See, e.g., Held, chapter 4, “Understanding Voice” and chapter 5, “Telephone Operations,” and Sheldon at pp. 959-968. The Internet can be any network or combination of networks that support packet-switching. Such a network can include, but is not limited to, a network supporting the Internet Protocol (IP) and related protocols. See, e.g., Held, chapter 2, “IP and Related Protocols,” and Sheldon, pp. 503-543.
VoIP systems allow a call originating from a PSTN to be carried over the Internet. In this way, voice traffic can be carried over the Internet bypassing more expensive long-distance carriers. For example, Toll Bypass Carrier services, multi-site corporations, and other users use VoIP systems to reduce the cost of long distance telephone calls to a fraction of one cent per minute.
Vendors provide a product or family of products to support VoIP. For example, Array Telecom Corp. of Herndon, Va., a wholly-owned subsidiary of Comdial Company, has provided an early generation of products that provide a multi-location, turn-key solution to VoIP (Array Tel Series 1000 and 2000, also called versions 1 and 2). See also B. McConnell, How to Build an Internet PBX, http://www.hellodirect.net/tutorial/ip-phone.htm, down loaded Aug. 16, 1999.
b. How Voice Over IP Telephony Works
A VoIP system typically relies on gateways to provide an interface between PSTN and IP networks. FIGS. 1A and 1B illustrate how a call is placed over the Internet. As shown in FIG. 1A, a user calls picks up a telephone 100 and dials a phone number of a phone 140. The called party at phone 140 answers. A connection is then established through gateways 110 and 130 over IP network 120. Voice, fax, and data transmission is then carried out between phones 110 and 140 through this connection. In this way, an expensive long-distance carrier on a PSTN can be bypassed.
FIG. 1B shows the operation of a conventional VoIP system in greater detail. A local PBX (private branch exchange) system 105 places a call originating from phone 100 over a PSTN to a local originating gateway 110. Note gateways 110 and 130 are referred to herein as originating and destination gateways for convenience only. In practice, full-duplex communication is carried out and either phone can originate or receive a call. Also, PBX system 105 is programmed to automatically (and selectively) route certain calls from phone 100 to gateway 110. In this way, a user can dial the destination phone number directly in one step. Alternatively, if no PBX or other special preconfiguration at a local exchange carrier (LEC) is performed, a two step process is used where a user calls gateway 110 directly and then in response to a prompt from gateway 110 enters the destination phone number of phone 140.
Next, gateway 110 contacts destination gateway 130 over IP network 120. Destination gateway 130 dials the destination phone number over a PSTN line to the destination phone 140. Gateway 110 then packetizes the voice stream from the PSTN and routes it over IP network 120 to gateway 130. Destination gateway 130 converts the data packets into a voice stream and sends it over a PSTN line to the called party at phone 140. By strategically locating gateways, such as gateways 110 and 130, in desired calling areas long-distance costs are substantially reduced. Indeed, a long-distance call is essentially replaced by two local phone calls and a low cost IP connection.
c. Shortcomings
Even though VoIP has created an enormous enthusiasm, the implementation and success of VoIP networks has been hindered due to at least following four (4) major shortcomings:                voice jitter caused by unpredictable bottlenecks of the Internet;        unacceptable voice quality due to poor compression techniques;        absence of advanced applications to offer services such as prepaid calling or carrier class global call routing; and        absence of switching functions such as trunk-to-trunk connections and PBX interfaces.        